Linux exe

It intrigues me that in my Linux OS, I launch OpenBVE using a command similar to "mono OpenBVE.exe".
The 'exe' extension is usually used to mark a Windows executable, which can't normally be run under Linux.
So what's going on here?

Think of Mono (The Linux version of Net) as an emulator similar to Wine, although the Wine team state it is not an emulator and maybe Mono isn't a real emulator either but just think of it as one that allows OpenBVE.exe to run.

Actually I think the correct description is probably "a runtime environment", such as Java is another "runtime environment". So Mono is a "runtime environment".

That makes sense- thankyou!
So really it is a misleading use of the 'exe' extension.